Patching compound



United States Patent 3,162,542 PATCH-KING COMPDUND Donald E. Christensen, Longview, Wash, assiguor to Weyerhaeuser Company, Tacoma, Wash, a corporation of Washington No Drawing. Filed June 5, i961, Ser. No. 115,044 5 Claims. (Cl. 106-200) This invention relates to a composition of matter that is useful for filling voids in the veneer core sheet of woodpaper laminates and specifically relates to a composition of matter comprising a cork-rich coniferous bark fraction, a bark fraction having cork as the major component thereof which has been taken from the bark of a coniferous tree, and a resin selected from the group consisting of a rosin, and a lime-treated rosin.

While it is desirable to use solid sheets of veneer for the core material in a wood-paper laminate so that there will be no voids in the core to form weak areas in the laminate, it is economically necessary to use grades of veneer which have these voids. It is, therefore, necessary to patch the veneer prior to incorporating it into the laminate. In the past this has been accomplished by removing a portion of the veneer from around the void and inserting a solid veneer patch in its place. Both the cut out portion and the patch were of predetermined shape. The procedure was both costly and time consuming.

It is an object of this invention to produce a thermoplastic material having many of the characteristics of wood.

It is another object of this invention to produce a thermoplastic material having good adhesion to wood and paper, together with toughness and absence of excessive softness.

It is also an object of this invention to make a material that is useful in filling the voids in veneer.

It is a further object of this invention to provide a composition of matter comprising a cork-rich coniferous bark fraction and a resin selected from the group consisting of a rosin, and a lime-treated rosin.

Various other anciilary objects and advantages of the present invention will become apparent from the following description and explanation.

i have found that the composition of matter comprising a cork-rich coniferous bark fraction in combination with resin selected from the group consisting of a rosin, and a lime-treated rosin is useful in filling the voids in wood veneer because it has properties closely resembling the properties of wood.

Bark is not a homogeneous material, but is composed primarily of three dilierent tissue components, to-wit: cork, sclerenehyma tissue in the form of either hast fibers or stone cells, and parenchyrna tissue made up chiefly of sieve tubes but containing also food storage cells, companion cells, and connecting ray tissues. The term nonfibrous phloem used herein refers broadly to that portion of the whole bark from which a substantial portion of the cork and the sclerenchyma tissue has been removed. it, therefore, includes parenchyma tissue and may also include small proportions of the cork and fibers which are incidentally broken and finely comrninuted to powder form during the diiierential pulverization of the bark.

The percentage composition of these three tissue components varies considerably with respect to the barks of dilierent species of trees; with respect to the barks of different trees of the same species, depending on the age of the tree, geographical location, and other such factors; and even from different portions of the bole of the same tree. An indication of the variation in content of tissue components of different species of trees will be seen from inspection of Table 1, below, showing a percentage analy "ice sis of three typical western coniferous trees, as follows: Douglas fir (Pseudotsuga taxifolia), western hemlock (T saga heterophylla), white fir (Abies concolor).

The analyses given in Table I, above, are but typical analyses and percentages of the components may vary greatly from one tree to another, or from one portion to another portion of the same tree. For instance, in a study made to determine the potential yield of Douglas fir cork, the bark from different trees or different portions of the same tree was segregated into four grades determined by the thickness of the cork layers, as follows: /4 to A; inch or more, 1 to 4 inch, to inch, and less than inch. The cork yield from the four grades, based on the averages of a large number of samples, was found to rangefrom 45% to 20%. The grade 1 bark having cork layers of A to /2 inch thickness was obtained mostly from the stumps of very old trees. The cork content in Abz'es coacolor bark was found to vary from about 6% in the case of trees ten inches or less in diameter to approximately 50% in trees from 12 to 16 inches in diameter, and then to decrease to as low as 29% in trees from 16 to 46 inches in diameter.

The bark components in forms suitable for the practice of the instant invention are obtainable by methods which rely upon the selective comminution of the bark constituents followed by the application of mechanical methods for separating the products of various particle size. Such methods are represented by those disclosed in Letters Patent Nos. 2,437,672 (granted March 16, 1948, to Herman W. Anway, for Method of Treating Bark), 2,446,551 (granted August 19, 1248, to Robert D. Pauley, for Separation of Pure Bark Fiber From Finely Comminuted Bark), and 2,627,375 (granted February 3, 1953, to Bror L. G rondal and Calvin L. Dickinson, for Separation of Bark Components); said Letters Patent having a common assignee with this application. These methods are based upon the discovery that when the whole bark is subjected to a pulverizing operation at a controlled moisture content, the non-fibrous components of phloem are relatively friable as compared with the cork and sclerenchyma. The whole bark is, accordingly, subjected to one or more comminuting operations at a controlled moisture content whereby the n-on-ibrous phloem is reduced to a powder, the fiber bundles are opened up to release the individual fibers, but the relatively resistant aggregates of cork cells comprising the cork layers are not substantially reduced in size. ere are thus produced three principal tissuecomponents having different particle sizes, i.e., cork, ultimate fiber, and powdered non-fibrous phloem. These may be separated by employing appropriate mechanical methods, such as screening, flotation, or air eparation, but not without difiiculty, and fractions designated as pure means as pure as obtainable by such methods.

While the cork component obtained from the bark of coniferous trees resembles cork from the cork oak, it is quite different therefrom in chemical composition and in some physical properties. It has been established that the cork component from the bark of coniferous trees is highly thermoplastic, whereas the cork of the cork oak is not. Whereas temperatures of between about 450 F. and about 600 F. are employed in the commercial production of cork tile and cork board from Mediterranean cork, Douglas fir cork flows and becomes thermoplastic at temperatures slightly above 300 F. In fact, if it is heated to temperatures of the order of about 430 F., it chars and decomposes, providing further evidence of the fundamental distinction between these two products.

A significant difference between the cork of coniferous trees and Mediterranean cork is observed in their bulk densities. When samples of Abies concolor, Douglas fir and Mediterranean cork were milled to approximately 14 mesh size, the bulk density of Abies concolor was 15.3 pounds per cubic foot, of Douglas fir cork was 11.7 pounds per cubic foot, and of Mediterranean cork was 3.5 pounds per cubic foot. Mediterranean cork contains 20% to 30% lignin, whereas Douglas fir cork contains approximately 50% lignin as determined by the 72% sulfuric acid method. Mediterranean cork contains 25% to 40% fatty acids, whereas Douglas fir cork contains approximately of these compounds. Mediterranean cork contains 3% to 6% tannins and phlobaphenes, Whereas Douglas fir cork contains to of water soluble tannins. Other characteristic of Douglas fir cork are that it contains approximately 9% of Wax; is approximately 65% soluble in ether; its aqueous suspension has a pH of 3.6; and it shows absorptive reactivity with formaldehyde.

This coniferous cork is the major component of the coniferous bark fraction of the invention. In the coniferous bark fraction that is. preferable for the present composition, the cork forms approximately 68% of the total fraction. This. amount can varyby as much as 5% in either direction because of the difficulties in separation of the various materials of the bark. It is also preferable that the particle size of this bark fraction should be such that 95% will pass through a 65 mesh screen and 65 Will pass through a 200 mesh screen.

Example 1 A mixture containing 60% of a cork-rich coniferous bark fraction from Douglas fir having the preferred composition previously specified and, 40% of a lime-treated resin was milled on heated rolls until it formed a composite mass. The material was then cooled, and subsequently ground to a particle size of between 1435' mesh. The particulate material was then used to patch voids in veneer by being placed in the void and subsequent 1y heated so that it flowed, filling the entire void, and then cooled'so that. it again (formed a composite mass. The material exhibited many of the properties of wood and adhered well to both Wood and paper. There was no noticeable chipping or breaking of the patches on either sawing or nailing.

Example 2 This material was made in the same manner as Example 1, except that the composition comprised 53% of the cork-rich coniferous bark fraction and 47% of a lime the spirit of the invention. It should, therefore, be under-,

stood that the examples cited and the methods of procedure set forth above, are intended to be illustrative only and are not intended to limit the scope of the invention.

I claim: I

1. A composition of matter consisting essentially o from 35 to by Weight of a coniferous bark fraction and from 55 to 35% by weight of a resin selected from the group consisting of rosin and lime-treated rosin, said bark fraction comprising at least 60% by weight coniferous bark cork mixed principally with sclerenchyma tissue.

2. A composition of matter consisting essentiallyof from 50 to 65% by Weight of a coniferous bark fraction and from 50 to 35% by weight of a resin selected from the group consisting of rosin and lime-treated rosin, said bark fraction comprising at least 60% by weight coniferous bark cork mixed principally with scelerenchyma tissue.

3. A composition of matter consisting essentially of from 50 to 60% by weight of a coniferous bark fraction and from 50 to 40% by weight of a resin selected from the group consisting of resin and lime-treated rosin, said bark fraction comprising at least 60% by weight coniferous bark cork mixed principally with sclerenchyma tissue.

4. A process comprising mixing 35 to 65 by weight of a coniferous bark fraction comprising at least 60% coniferous bark cork mixed principally with sclerenchyma tissue with a resin selected from the group consisting of rosin and lime-treated rosin, heating such substance until it fuses into a mass, cooling said substance and grinding said substance into a particulate material.

5. The composition of claim 1 in which said matter is a particulate material.

References Cited in the file of this patent UNITED STATES PATENTS Jorgensen May 26, 1959 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF FROM 35 TO 65% BY WEIGHT OF A CONIFEROUS BARK FRACTION AND FROM 55 TO 35% BY WEIGHT OF A RESIN SELECTED FROM THE GROUP CONSISTING OF ROSIN AND LIME-TREATED ROSIN, SAID BARK FRACTION COMPRISING AT LEAST 60% BY WEIGHT CONIFEROUS BARK CORK MIXED PRINCIPALLY WITH SCLERENCHYMA TISSUE. 